I have a Sips house in rough and I am using two Panasonic Whisper Green fans, one to ventilate the home and the other to circulate the conditioned air from the ductless mini-split in the main living area back into the bedrooms.

The fans will run continuous at 50, 70, 90, and 110 cfm and can be turned on high with a separate switch to 130 cfm.

The ventilation fan picks up in each of the two bathrooms and the laundry room with adjustable ducts.  I plan to ventilate 20 cfm continuous in each bathroom and pick up another 10 cfm from the laundry which will meet my ventilation levels for this 1560 sq ft home.

I plan on circulating 20 cfm to each of the smaller bedrooms and 30 cfm to the master bedroom to distribute the heating and cooling from the mini-split.  As both fans are adjustable, I can vary the air delivery to some degree.

All ducts are in dropped ceilings inside the envelope of the home except the exhaust duct.

Has anyone else had experience with any of this?  Any comments?

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Time will tell whether or not the circulation fan is needed, and if so at what level of air movement. It sounds like you are using one fan to do the circulating, probably installing it near the mini-split indoor unit, and wye'ing the outlet duct to go to the three bedrooms. I'm not sure what you mean by "adjustable ducts"... presumably some type of inline dampers? 


Overall, it seems wise to have some facility for moving air around, if there's only one point heat source. I've been contemplating the same thing for my house, where I will probably install a mini-split shortly but wonder if the bedrooms will get enough heat.


This is the adjustable duct grill I will be using.  The center screws in and out to adjust flow.  It comes in a number of sizes and slips inside a 6" round duct at trim.

I will also install transfer grills over the doors so when te doors are closed, circulation can still take place.  Pretty exciting!


Tyson, it looks like you tried to post a link there, but I can't see it. I'd like to know what it is, I think we are working on similar issues.

I tried to add a picture of the adjustable 6" vent grills I am using.  Here is a link.




Let me know what you think.

Got it. Just for reference, here is another source of similar products. I get them through Air Commodities in Seattle.



This has been done successfully in numerous places.  Steven Winter Associates did a project in Massachusetts where there was a sealed combustion heater in the main living space and a Panasonic 80 cfm DC fan used in the living room ceiling to circulate warm living room air to the bedrooms.  It worked quite well.  Rated at less than 0.3 sone, the fan only draws 12 watts at 60 cfm, with 30 cfm to each bedroom.  Temperatures were quite even if the bedroom doors were open or a transfer grille is used.
Thanks Don.  I can't wait to test the fans for static pressure, watts and actual air flow with the duct configuration I have.  The more I hear from the blogs I am participating on, the more confident I am on the right track.  Here in Washington, WSU Energy Extension provides code support and is the SCO for Energy Star.  One of their own was  in town yesterday and told me about his 1,600 sq ft two story conditioned by a single Fujitsu 18,000 BTU mini-split.  He wired for bedroom wall heaters just in case but has never put them in.  To him, the small temperature differentials are well within his range of comfort, and this in in a home that started at 20 ACH and is now down to a little over 5 ACH.  My home will probably be 1 ACH or lower.  If possible, I would like to loose the room heaters if they are not needed.  It would get me closer to standard construction costs after the savings on the mechanical equipment you would normally have to install.  Also,  If it ever did get cold enough to need more heat, the gas fireplace is right next to the pick up fans for the bedrooms.  Might as well get some practical use out of it.
That sounds like a good technique to me. Those whisper green fans are pretty good pieces of equipment.

Sounds pretty neat.  Couple questions jump into my head:


Did you perform room by room load calc?  Have you calculated airflow delivered, or assuming airflow based upon fan rating?  


Is the exhaust fan an erv, or are you using a forced infiltration approach?  


Have you considered how you will deal with moisture?  


I would probably prefer a dehumidifying ERV system (ideally with heating and cooling built in), pulling from the bath's & kitchen and delivering to the bedrooms.  If an erv for heating, cooling, and dehumidification can't be found, I'd lean toward  2 indoor units on the mini-split, one in the living area and one in the far bedroom.  

I recently visited some houses in Fresno that had two ducted minisplits in the hall ceiling with our WhisperComfort ERV next to the return for both of them (I am the National R&D Manager for Panasonic).  The minisplits were side-by-side pointed in opposite directons, one for the bedrooms and one for the living room/kitchen end of the house.  The tempered air from the ERV was mixed with room air and pulled into the minisplits and distributed throughout the house.  It seemed to work well in the 20 or so houses he had purchased through foreclosure and then performed an energy retrofit.

No room by room calcs yet but no bedrooms have significant south and or west exposure.  Also, I got board caulking everything and defaulted to flash sealing the entire lid with R-49 cellulose inside of raised heal trusses.  Others I have talked to have yet to turn on thier electric room heaters and are reporting comfortable rooms with little or no investment in circulation, save a jumper fan for a south west room with or without a west facing window.  I work with the energy star gurus in the northwest and my HVAC hero visited the home and expected no issues.


I am assuming air flow based on rating .  With no experience my assumptions are that static pressure will not overly tax the fans ability to deliver air resembling its stated ability under desirable conditions.  This would leave me a margin of error in the neighborhood of 50% if I cap the flow to the kitchen which is the least likely room to need additional circulation for comfort.  Also, I am using exhaust only ventilation with a central fan pulling half of the required air from the master bath continuos.  This should air in getting circulation around that last corner to the master bath and help pull addition conditioned air into the master bedroom itself.

I opted for exhaust only ventilation.  With humidity levels in the mid thirties, that has never been an issue in our area.  When I calced out the cost savings for an erv system, exhaust only won out on my initial cost of construction goal being close to regular stick frame.


I am pulling from the bathrooms and laundry with my exhaust only system. Two pick ups in the master and one each in the laundry and main bath.  With a required ventilation of about 46 cfm continuous, I can meet the ventilation requirements of the bathrooms at the same time.  Here's the twist!  I am using the same fan for the exhaust system.  The characteristics of the Whisper Green 130 were too hard to resist.  I mounted it on a 10 by 14 by 20 inch duct box and installed two six inch ports.  one port feed the master bath with 6 inch flex that y's toward the end of the run and the second port y's to the laundry room and the main bath.  As I will require the fan to deliver only 50-70 cfm continuous to meet code, I have the 90-110 settings as buffer if static pressure becomes an issue.  Lastly the high setting will be switched in parallel to allow the fans to be ramped up when the user of the bathrooms feels like it.  I have a sealed access door on one end of the box to access the settings and service the fan.  It all sounds like a Cinderella story to me up until the time I discover that static pressure has overcome the fans ability to deliver anything close to it's rating.  My back up is to yank the fan and install a 6" inline just above the location of the existing one.  Also,I dropped the lid in the kitchen and all ducts except the exhaust 6" coming off of the vent fan are in conditioned space.  This is one clean attic.  I will post a  few pictures after a soak in the hot tub.  I spent the day in attics QC'ing the beginning of about 200 blows that are generally out of compliance on 3-6 out of 9 utility program requirements.

Please continue with questions.  Still looking forward to your predictions when yo have enough info.



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